Emit declared build parameters into build-graph.json

[ChrisonSimtian]

Problem

build-graph.json (the editor-tooling contract in BuildGraphUtility) carries only targets. The build's [Parameter]/[Secret] members — e.g. NuGetApiKey on IPublish, the set dotnet fallout --help lists — never reach the VS Code extension, so it can't surface them.

Outcome

Additive parameters[] in build-graph.json, projected from the build's declared parameters. Schema stays v1 (new field is backward-compatible):

{ "name": "NuGetApiKey", "secret": true, "description": "…", "declaredIn": "IPublish" }

Acceptance criteria

• All declared [Parameter] members are projected, including inherited component params (IPublish, etc.) — matching --help's set.
• [Secret] members flagged secret: true.
• Fields: name, secret, description, declaredIn.
• SchemaVersion unchanged (additive); existing consumers unaffected.
• BuildGraphUtilitySpecs updated to cover the projection.

Context: [ADR-0009] run-config discussion; feeds the extension issue below.